Tracking Bins Moving Down a roller conveyor

I am adding an inspection system on an existing conveyor. The idea is that if the bin contains a defect it will fail inspection and once it reaches the end of the conveyor I will flag it so that our automated carts pick it up and take it to a partial bin area to be handled correctly instead of being put up in our warehouse. The conveyors use photo eyes at every conveyor segment to index the bin and there are 10 segments after the inspection. I am trying to figure our the most reliable way to track the bin until it reaches the end of the rollers. I need to know when the first bin arrives, but I also need to be able to track the next bin if it for some reason has the same defect. This is tough to explain, but I am hoping someone here who is more experienced here can guide me through the easiest way to achieve this. (Studio 5000) Thanks!

First, a couple of parameters:

Can a bin be manually removed from the conveyor after it is inspected but before it reaches the "flagger"?

Can multiple bins fit on each conveyor section and if so how many?

Keith

In this particular situation no bins will be manually removed from the system once I inspect and the move down the line. Only one bin per conveyor section at a time.

I did that long time ago with a FIFO queue.

Never, never a bin can be manually removed from conveyor.

You FIFO queue size must be bigger that the amount of of bins that can be located in your conveyor section.

When a fail is detected that bin must be "marked" by software at FIFO entry, so that can be easily identified when approaching conveyor exit thru FIFO data.

In my case I use a counter to mark each bin and a bool to signal a fail bin, when a bad bin is found at exit I installed a kicker to get rid of a that bin.

I would suggest using some kind of reflector that inspection can easily attach to the bin for flagging defects. Then at the end of the line position a photo-eye that would detect and reject the flagged bin. One draw back to this solution is you need to collect reflectors and return to inspection point. This would be a dirty but inexpensive solution.

FIFO's work great but it's not if but when they get off for some unforeseen reason. Then you must somehow find a way to correct the FIFO.

Are the bins reuseable? If so, you could barcode them, and flag bins to be removed by individual numbers. Barcode scanners aren't that expensive, but there's some setup involved. If the bins are single-use, though, this may not be an option, but in that case perhaps you could flag them with a paint mark or something similar.

I've done this with a FIFO as well, but it was on a machine that had fixed nests for each part, and I could track nests instead of parts so there was no chance of the FIFO getting off on its count. It also required a lot of work to figure out which parts had not been inspected during startup/shutdown and get those rejected.

I have done many tracking systems, some quite simple some far more complicated, the simple one was a pick & place rotating table where parts were assembled in nests there were 12 nests (1 for loading, 3 for checking & 1 for unloading). We had a shift register of integers incremented on index so 0 = empty, 1 =part present, 2 part ok, 3 part faulty, 4 part not removed, I cannot remember exactly but seem to remember 10, 20, 30, 40 = part not removed second time round & 50, 60, 70, 80 for 3rd time round and would stop the machine and alarm.
The other one was a very long ring conveyor where the bin would enter the ring and a bar code read, this would then divert down one of 16 legs based on bar code ready for loading, if it missed a read then this was dumped onto the 17th leg, there was also a weigh station so should a bin be over weight (H&S) this would be marked with an ink jet.
It is quite simple just a simple shift register for example 0 = no bin (assume empty start), 1 = good bin 2 = bad bin, if you have an HMI then you could have these registers on an engineering page so they could be cleared or modified in the event of a problem. (always remember have a way back).
Even simpler, if only good or bad and only say 16 stations could use an array of bits.

Great video here, written by Garry

https://www.youtube.com/watch?v=K1j6HvNF-5s

Thank you all for the responses. I implemented a FIFO this morning and it appears to be accomplishing what I needed. Being fairly new in all this I am still learning some of these instructions. As it sits now when a bin rolls under my camera system it inspects the bins for defects. The FIFO stores the inspection results. At the end of my conveyors I am unloading the FIFO as the bins existing barcode is being read. If when the FIFO is unloaded and my bin failed inspection I will overwrite the Barcode scan results with a set of my own. This will make our automated forklifts (LGVS) take the bin to a maintenance area instead of storing it in our warehouse. Thank you all for the help!

I did this for a walking beam system with multiple stations.
do 2 things. each is a backup of the other.
create an 11 word array.
create a int word.


at the inspection station, inspect the part.
if it fails, put 999 into the word array (word 11)and put a 1 in bit 11 of the int word.
as the bin moves down, shift the word to the next lowest word array. also shift the bit to the next lowest bit.
at the unload station, if either if these is not zero, reject the bin.
I moved the words and did a bit shift on the bits.
james